Counterbalanced reciprocating mechanism

ABSTRACT

The motor drives the crown gear which has an upwardly projecting eccentric drive pin which drivingly engages the channel fixed on the spindle which reciprocates in the fixed tube and supports a saw blade. The induced vibration is counterbalanced by the reciprocating counterbalance which slides on the outside of the tube. The crown gear has a cylindrical drive member which engages the cylindrical hole in the transfer block. The transfer block is moved in an orbital path and the opposed parallel sides engage and reciprocate the counterweight. The crown gear and cylindrical drive member have material removed to counterbalance the two drives.

This invention relates to reciprocating saws of the type using aneccentric drive. Saws of this type develop considerable vibration. Thisinvention is directed to reducing such vibration.

CROSS REFERENCE TO COPENDING APPLICATION

My application Ser. No. 541,093 filed Jun. 20, 1990, .Iadd.now U.S. Pat.No. 5,025,562, .Iaddend.as a continuation-in-part of Ser. No. 487,219filed Mar. 1, 1990, .Iadd.now abandoned, .Iaddend.shows an in-line sawusing a counterbalanced wobble plate drive.

SUMMARY OF THE INVENTION

This invention provides a pinion gear driving a crown gear which has aneccentric drive to the shaft on which a saw blade is mounted. The crowngear also has an eccentric drive to a counterbalance, the saw blade andthe counterbalance reciprocate 180 degrees out of phase, thusessentially eliminating all vibration.

More specifically, this invention provides an eccentric drive to a sawblade to reciprocate the saw blade while at the same time reciprocatinga counterbalance. The eccentric drive of the saw blade is somewhatconventional. The spindle which supports the saw blade reciprocatesinside a tube fixed in the housing. A counterbalance mass reciprocateson the tube and is prevented from rotating about the tube. The crowngear is provided with a cylindrical drive which is eccentric to thecenter of the crown gear. This cylindrical circular drive engages thecounterbalance which, as noted, is constrained to reciprocating motion.The momentum of the counterbalance and the combined momentum of thespindle and a typical saw blade are essentially equal so the vibrationis cancelled. Material is removed from the crown gear and cylindricaldrive member to ensure that the crown gear, the eccentric drive and thecylindrical drive are balanced and do not set up lateral vibration.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation view of a reciprocating saw provided withthis invention.

FIG. 2 is a vertical section through a portion of the saw shown in FIG.1.

FIG. 3 is a horizontal view taken on line 3--3 in FIG. 2.

FIG. 4 is an exploded perspective view of the main parts of the drivefor the spindle and the counterbalance.

DETAILED DESCRIPTION OF THE DRAWING

The reciprocating saw shown in the drawings has a gear case 10 on thefront of handle portion 12. Drive motor 14 has a drive shaft 16 withgear 18 driving crown gear 20 which is fixed on shaft 22 by key 24.Shaft 22 is rotatably mounted in bearings 26, 28 fixed in the gear case10. Bearing 26 is retained in the case by annular plate 30 held in placeby screws 32.

Spindle 34 on which saw blade 36 is mounted in the usual mannerreciprocates in tube 38 which has its ends fixed in the gear case. Thebottom portion of the tube is cut away as indicated by the dashed line40 in FIG. 2 to allow the inverted channel 42, which is connected to thespindle 34 by fastener 44, to move between the ends of the cutout. Afirst or primary eccentric drive means, reciprocates the spindle. Thisdrive means includes eccentric drive pin 46 which projects upwardly fromthe top of the crown gear and has a square drive block 48 mountedthereon on roller bearings 50. The opposed sides of the block slideablyfit inside the depending legs of the inverted channel. The flat sides ofthe block minimize the loading between the drive pin and the channel tothereby reduce wear. As the crown gear rotates, the eccentric drive pinand block force the channel and spindle to reciprocate in the tube 38.

A secondary or second drive means reciprocates the counterweight andincludes a cylindrical drive member 52 which projects upwardly from thetop of the crown gear and is eccentric to the center of the crown gearin the direction opposite the eccentricity of the pin. This cylindricalmember engages cylindrical hole 54 in the generally square transferblock 56. Block 56 engages the depending legs 58, 58 of counterweight 60which slides on the outside of tube 38. Since there is a substantialsurface contact between the block and the legs of the counterweight wearis minimized. If desired, a ring bearing can be provided between thecircular drive member and hole 54 in the block.

It will be noted that the crown gear and cylindrical drive member have acrescent shaped cutout 62 to reduce material and counterbalance both theblock 56 and the cylindrical eccentric drive member/gear about the gearaxis. It is well to keep in mind that the crown gear and the associatedeccentric drives (pin 46 and cylindrical member 52) and the transferblock 48 are effectively a unitary rotating mass and the removal of thematerial in the cutout can balance the mass. Thus, the counterbalance 60counterbalances the spindle and saw blade while the eccentric drives forboth the spindle and the counterbalance are counterbalanced to avoidinducing vibration either parallel to or transverse to the spindlemotion.

I claim:
 1. A reciprocating drive mechanism comprising,a housing, aspindle mounted in said housing for reciprocating motion, acounterweight mounted in said housing coaxial with said spindle andmoveable relative to said spindle, .[.eccentric.]. drive means forreciprocating said spindle.[., eccentric drive means.]. .Iadd.and.Iaddend.for reciprocating said counterweight in the direction oppositethe direction of said spindle so the axial forces induced byreciprocation of the spindle are substantially cancelled, .[.with bymeans counterbalancing said drive means.]. .Iadd.said drive meansincluding a transfer block reciprocating one of said spindle and saidcounterweight and having therethrough a hole, said hole having a centrallongitudinal axis transverse to the direction of reciprocation of saidspindle, and said drive means further including a cylindrical memberhoused in said hole for rotation relative to said transfer block, saidcylindrical member reciprocating the other of said spindle and saidcounterweight..Iaddend.
 2. A reciprocating drive mechanism according toclaim 1 in which the spindle supports a tool and the axial forcesinduced by the stroke and mass of said counterweight approximate theaxial forces induced by the stroke and combined mass of said spindle andsaid tool. .[.
 3. A reciprocating drive mechanism comprising,a housing,a spindle mounted in said housing for reciprocating motion, acounterweight mounted in said housing for reciprocating motion relativeto said spindle, said spindle and said counterweight being concentric,and first eccentric drive means for reciprocating said spindle andsecond eccentric drive means for reciprocating said counterweight inopposite directions so the axial forces induced by reciprocation aresubstantially cancelled..].
 4. A reciprocating drive mechanismcomprising,a housing, a drive motor in said housing, a spindle mountedin said housing for reciprocating motion, a counterweight mounted insaid housing .Iadd.coaxial with said spindle .Iaddend.for reciprocatingmotion .[∥]. .Iadd.relative .Iaddend.to .[.and concentric with.]. saidspindle, first and second eccentric drive means driven by said motor andconnected to said spindle and said counterweight respectively, said.Iadd.first and second .Iaddend.drive means being operative toreciprocate said spindle and said counterweight in oppositedirections.Iadd., said second drive means including an eccentriccylindrical drive member and a transfer block having a hole engaged bysaid cylindrical drive member to be driven by said cylindrical drivemember in an orbital path, said transfer block slideably engaging saidcounterweight to cause said counterweight to reciprocate..Iaddend.
 5. Adrive mechanism in accordance with claim 4 in which the mass and strokeof said first drive means and said spindle are proportioned relative tothe mass and stroke of said secondary drive means and said counterweightso the axial forces induced by reciprocation are substantiallycancelled.
 6. A drive mechanism in accordance with claim 5 in which saidfirst and second eccentric drive means are counterbalanced.
 7. A drivemechanism in accordance with claim 6 including a guide sleeve mounted insaid housing,an axial slot in said sleeve, said spindle being slideablymounted in said sleeve, said first drive means projecting through saidslot in said sleeve to drivingly engage said spindle.
 8. A drivemechanism in accordance with claim 7 in which said counterweight ismounted on said sleeve for reciprocating motion.
 9. A drive mechanism inaccordance with claim .[.8.]. .Iadd.4 .Iaddend.in which said .[.seconddrive means includes an eccentric cylindrical drive member, a.]..Iadd.counterweight includes a pair of legs defining parallel surfacesspaced apart in the direction of reciprocation of said counterweight andrespectively extending perpendicularly to the direction of reciprocationof said counterweight, in which said .Iaddend.transfer block .[.having ahole engaged by said cylindrical drive member to be driven by saidcylindrical drive member in an orbital path, said block having opposedparallel sides slideably engaging said counterweight to cause thecounterweight to reciprocate on said sleeve.]. .Iadd.is housed betweensaid surfaces, and in which said legs restrain said transfer blockagainst movement relative to said counterweight other than in thedirection perpendicular to the direction of reciprocation of saidcounterweight. .Iaddend. .[.
 10. A reciprocating saw in accordance withclaim 9 in which the mass and stroke of said primary drive means andsaid spindle are proportioned relative to the mass and stroke of saidsecondary drive means and said counterweight so the axial forces inducedby reciprocation are substantially cancelled..]. .[.11. A reciprocatingsaw in accordance with claim 10 including means for counterbalancingsaid primary and secondary eccentric drive means..]. .[.12. Areciprocating saw in accordance with claim 11 including a guide sleevemounted in said housing,an axial slot in said sleeve, said spindle beingslideably mounted in said sleeve, said primary drive means projectingthrough said slot in said sleeve to drivingly engage said spindle..]..[.13. A reciprocating saw in accordance with claim 12 in which saidcounterweight is mounted on said sleeve for reciprocating motion, saidcounterweight including a recess receiving said secondary drivemeans..]. .[.14. A reciprocating saw in accordance with claim 13 inwhich said second drive means engages said counterweight..]. . Areciprocating saw comprising,a housing .[.including a gear case.]., .[.amotor in said housing and having a motor shaft, a pinion gear on saidshaft, a crown gear mounted in said housing and driven by said piniongear,.]. a spindle mounted in said .[.gear case.]. .Iadd.housing.Iaddend.for reciprocating motion .Iadd.along a first axis.Iaddend., acounterweight mounted in said .[.case.]. .Iadd.housing .Iaddend.forreciprocating motion .[.parallel to and concentric.]. .Iadd.coaxial.Iaddend.with said spindle, .[.primary and secondary eccentric.]..Iadd.first .Iaddend.drive means .[.mounted on said crown gear andconnected to said spindle and said counterweight respectively,.]..Iadd.for reciprocating said spindle, .Iaddend. .[.said primary andsecondary.]. .Iadd.second .Iaddend.drive means .[.operating toreciprocate said spindle and.]. .Iadd.for reciprocating .Iaddend.saidcounterweight in .[.opposite directions.]. .Iadd.the direction oppositethe direction of said spindle, said first and second drive meansincluding a gear mounted in said housing for rotation about a secondaxis, a cylindrical member eccentrically mounted on said gear, a driveblock on said cylindrical member, rotatable about a third axis parallelto and spaced from said second axis, the third axis rotating about thesecond axis, an inverted channel having a slot extending perpendicularlyto said first axis, said slot being engaged by said drive block, and atransfer block having a hole housing said cylindrical drive member, saidcylindrical drive member driving said transfer block in an orbital path,said transfer block having a side slideably engaging and reciprocallymoving one of said counterweight and said spindle along the first axis,such that said side remains perpendicular to the first axis while saidgear rotates, said inverted channel engaging and reciprocally moving theother of said counterweight and said spindle along the firstaxis.Iaddend..
 16. A reciprocating saw comprising,a housing .[.includinga gear case.]., a motor in said housing .[.and having a motor shaft, acrown gear rotatably mounted in said housing and driven by said motorshaft.]., a spindle mounted in said .[.gear case.]. .Iadd.housing.Iaddend.for reciprocating motion, .[.first eccentric drive meansconnecting said crown gear to said spindle to reciprocate said spindleas said crown gear is rotated,.]. a counterweight mounted in said.[.gear case.]. .Iadd.housing coaxial with said spindle .Iaddend.forreciprocating motion .[∥]. .Iadd.relative .Iaddend.to .[.and concentricwith.]. said spindle .[.axis.]., .[.a second eccentric.]. drive means.[.connecting said crown gear to.]. .Iadd.driven by said motor andrespectively connected to said spindle and .Iaddend.said counterweight,said .[.first and second eccentric.]. drive means .[.being offset withrespect to each other so the forces induced by reciprocation of thespindle is counterbalanced by the counterweight.]. .Iadd.including atransfer block reciprocating one of said spindle and said counterweightand having therethrough a hole, a cylindrical member having a cylinderaxis, and means for eccentrically driving said cylindrical member aboutan axis parallel to and spaced from said cylinder axis, said cylindricalmember being housed in said hole to drive said transfer block in anorbital path, said cylindrical member reciprocating the other of saidspindle and said counterweight.Iaddend.. .Iadd.17. A reciprocating drivemechanism according to claim 1 and further comprising a motor in saidhousing gear mounted in said housing for rotation about an axis anddrivingly engaged by said motor, and wherein said cylindrical member iseccentrically mounted on said gear with its cylinder axis parallel toand spaced from the axis of rotation of said gear..Iaddend. .Iadd.18. Areciprocating saw in accordance with claim 15 wherein said transferblock engages said counterweight and wherein said inverted channelengages said spindle..Iaddend. .Iadd.19. A reciprocating saw inaccordance with claim 18 in which the mass and stroke of said firstdrive means and said spindle are proportioned relative to the mass andstroke of said second drive means and said counterweight so the axialforces induced by reciprocation are substantially cancelled..Iaddend..Iadd.20. A reciprocating saw in accordance with claim 19 and furtherincluding means for counterbalancing said first and second drivemeans..Iaddend. .Iadd.21. A reciprocating saw in accordance with claim20 wherein said means for counterbalancing said first and second drivemeans comprises said cylindrical member having therein acutout..Iaddend. .Iadd.22. A reciprocating saw in accordance with claim21 and further including a guide sleeve mounted in said housing, whereinsaid sleeve includes an axial slot, wherein said spindle is slideablymounted in said sleeve, and wherein said first drive means protectsthrough said slot in said sleeve to drivingly engage saidspindle..Iaddend. .Iadd.23. A reciprocating saw in accordance with claim22 in which said counterweight is mounted on said sleeve forreciprocating motion, said counterweight including a recess receivingsaid second drive means..Iaddend. .Iadd.24. A reciprocating drivemechanism comprising,a housing, a drive motor in said housing, a spindlemounted in said housing for reciprocating motion along a first axis, acounterweight mounted in said housing for reciprocating motion relativeto said spindle along an axis parallel to said first axis, first andsecond eccentric drive means driven by said motor and connected to saidspindle and said counterweight respectively, said first and second drivemeans being operative to reciprocate said spindle and said counterweightin opposite directions, said second drive means including an eccentriccylindrical drive member and a transfer block having a hole engaged bysaid cylindrical drive member to be driven by said cylindrical drivemember in an orbital path, said transfer block slideably engaging saidcounterweight to cause said counterweight to reciprocate..Iaddend.